Page 14 - Highway Engineering Handbook Building and Rehabilitating the Infrastructure

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PREFACE TO THE THIRD EDITION

Improvements in highway design methods and practices are reflected in this Third Edition of the handbook.
The chapter on environmental issues has been updated throughout in view of ever-evolving regulations in that
area. The chapter on highway design includes information from the latest AASHTO “Green Book.” The trend
to replace bridges with spans up to about 60 ft (18 m) with stiffened special long-span corrugated steel and
precast concrete drainage structures is documented in the chapter on culverts. The chapter on safety systems
shows the trend to use median barriers over wider median widths than in the past. Metric units have been
added throughout the text and in tables and figures wherever feasible.
The reader is cautioned that independent professional judgment must be exercised when information set
forth in this handbook is applied. Anyone making use of this information assumes all liability arising from
such use. Readers are encouraged to use the latest edition of referenced specifications and guides, because
they provide more complete information and are subject to frequent change.
Roger L. Brockenbrough, P.E.